Create MQTT sensor for presence detection of BLE devices

AFAIK there has been an unanticipated certificate change on the GitHub side, as described in the 1.8.0 release notes

I only ever use the PlatformIO OTA installs anyway, as I’m using custom environments, so for any only awkwardly reachable gateway this might be the best option.

With the newly changed certificate this should not be an issue again in the future.